Grammy Award-winner Jason Isbell will hold a free concert on Saturday to rally support for Doug Jones, the Alabama Democrat reaching for victory in next week’s Senate race.

Ms. Isbell, a singer-songwriter known for his solo work and tenure with The Drive-By Truckers, will perform in Huntsville before voters hit the polls on Tuesday.

Mr. Jones is vying with Republican Roy Moore, a former judge accused of pursuing dates with teenage girls when he was in his 30s.

Mr. Moore denies the accusations, which have roiled the Republican party.

Many in the GOP have distanced themselves from Mr. Moore and called on him to drop out, giving Mr. Jones hope he can pull off an upset in the deep-red state.

The Moore campaign has been defiant, however, and President Trump is now openly endorsing him, saying Republicans can’t afford to have a “liberal” like Mr. Jones knock the GOP majority from 52 to 51 votes.

Mr. Isbell is an Alabama native who’s been openly critical of Mr. Trump on Twitter.

The Jones campaign said concertgoers won’t have to pay anything but should RSVP ahead of time.